Notation

    +----+           +=========+
    |    | One Byte  |         | Multiple bytes
    +----+           +=========+

        0        1
    +--------+--------+
    |00001000|00000010|
    +--------+--------+
     ^        ^
     |        |
     |        + less significant byte = 2
     + more significant byte = 8 × 256

    +--.--.--.--.--.--.--.--+
    |  :  :  :  :  :  :  :  |  Bits in one byte
    +--'--'--'--'--'--'--'--+

Contour Layer

	+---+---+=========+===========+===========+======================+
	|nPoints|  Flags  |   XData   |   YData   |      Poly Data       |
	+---+---+=========+===========+===========+======================+

Flags array

	Array of flags for each point in the outline. See below for details
	regarding the number of flag array elements.

	+--.--.--.--.--.--.--.--+ - - - - - - - - - - - - +
	|SC:RP: XT  : YT  : ZT  |  Repeat Number (RP = 1) |
	+--'--'--'--'--'--'--'--+ - - - - - - - - - - - - +

	 + ZT : The type of this point. The valid numbers are:
	   - 00 : On-curve point
	   - 01 : Quadratic off-curve point
	   - 10 : Cubic beginning off-curve point
	   - 11 : Cubic ending off-curve point
	 + XT and YT : The type of dX and dY data. The valid numbers are:
	   - 00 : The dX or dY is zero. No bytes needed.
	   - 01 : The dX or dY is encoded with two bytes, as a signed short.
	   - 10 : The dX or dY is encoded with one byte, as a byte, and the sign of
	          this entry is positive.
	   - 11 : The dX or dY is encoded with one byte, as a byte, and the sign of
	          this entry is negative.
	 + SC : This point is a beginning point of a contour. Only points with
	        ZT = 00 or ZT = 01 could set this flag to on.
	 + RP : Repeat this flag for N additional points, while N is provided in the
	        next byte.

XData and YData

	Contour point X and Y coordinates. See below for details regarding the
	number of coordinate array elements. Coordinate for the first point is
	relative to (0,0); others are relative to previous point.

Poly Data

	+----+----+===========+==================================+
	| Header  |  Masters  | Packed per-master variation data |
	+----+----+===========+==================================+

	+ Header : A packed field with:

		+---.-.-.-.-.-.-.-+-.-.-.-.-.-.-.-+
		|LMN:      Number of masters      |
		+---'-'-'-'-'-'-'-+-'-'-'-'-'-'-'-+

	  - LMN : Whether the master indeces in the "Masters" segment being uint32s.
	  - Number of masters : A 15-bit unsigned integer indicating the number of
	    masters for this layer.
	+ Masters : An array of uint16 or uint32s (determined by the LMN field in
	  the Header), representing master IDs
	+ Shared points : Optional (determined by SPZ). When present, a PointList is
	  placed here to indicate the points being affected by variations.
	+ Packed per-master variation data:

		+===============+==============+==============+==============+
		| Point numbers | X delta data | Y delta data |  Link data   |
		+===============+==============+==============+==============+

	  For "Point numbers", "X delta data" and "Y delta data", See the current
	  definition in GVAR, however the "Point number" list now indicates the
	  points that its "whether touch" flag being flipped in this master.

	  The "Link data" is used to represent "early" linking/IPs.

		+----+----+=======================+
		| nTerms  | Link/IP Reclord list  |
		+----+----+=======================+

		Link/IP Reclord
		+-.-.-.-.-.-.-.-+----+----+------+------+...
		|0:Y: nFollow-1 | refPtid | followPtId ...          (Linking)
		+-'-'-'-'-'-'-'-+----+----+------+------+...
		   ^
		   |
		   }-- Link/Interpolate X coordinate (0) or Y coordinate (1)
		   |
		   v
		+-.-.-.-.-.-.-.-+----+----+----+----+------+------+...
		|1:Y: nFollow-1 | rupPtid | rdnPtid | followPtId ... (Interpolate)
		+-'-'-'-'-'-'-'-+----+----+----+----+------+------+...

	  An IUP is performed after reading each tuple.

Reference Layer

                                  |<--     Optional    -->|
	+----+----+-------+--+--+--+--+--+--+--+--+--+--+--+--+===============+
	|   GID   | Flags |  X  |  Y  |  a  |  b  |  c  |  d  | Ref Poly data |
	+----+----+-------+--+--+--+--+--+--+--+--+--+--+--+--+===============+

	+ GID : The index of reference
	+ Flags :

		+---.---.---.---.---.---.---.---+
		|        RESERVED       :TFM:RND|
		+---'---'---'---'---'---'---'---+

	  - TFM : Whether the transformation terms (a, b, c, d) are provided.
	  - RND : Whether round this reference to grid.
	  - Ref Poly data : Identical to contour poly data, excluding:
	    - IUP mechanism.
	    - The point numbers entries are useless, since we are always modifying
	      the point attaches this reference.